A seemingly divided Supreme Court on Monday weighed a potentially costly challenge to the pharmaceutical industry's practice of not paying overtime to its sales representatives.

The justices questioned whether the federal law governing overtime pay should apply to the roughly 90,000 people who try to persuade doctors to prescribe certain drugs to their patients.

Many sales jobs are exempt from overtime pay under the Fair Labor Standards Act. But unlike typical salespeople who often work on commission, pharmaceutical sales representatives cannot seal a deal with doctors. Federal law, in fact, forbids any binding agreement by a doctor to prescribe a specific drug.

Two salesmen who once worked for drug maker GlaxoSmithKline filed a class-action lawsuit claiming that they were not paid for the 10 to 20 hours they worked each week on average outside the normal business day. Their jobs required them to meet with doctors in their offices, but also to attend conventions, dinners, even golf outings.

Justice Ruth Bader Ginsburg was among several justices who wondered about limits on overtime opportunities if the court were to rule for the sales reps. A court filing by the industry said drug companies could be on the hook for billions of dollars in past overtime.